Template-free synthesis of highly ordered 3D-hollow hierarchical Nb₂O₅ superstructures as an asymmetric supercapacitor by using inorganic electrolyte

Nb₂O₅ appeared as a promising candidate for a large number of applications. In the present work novel, 3D-hollow hierarchical Nb₂O₅ superstructures are prepared by self-organization of mesorods. The work emphasizes on the synthesis and detailed investigation of 3D-hollow hierarchical Nb₂O₅ superstructures, which are attained by two-step, template-free hydrothermal synthesis route. The obtained orthorhombic(T)-Nb₂O₅ superstructures have shown a high crystallinity, with a wide band gap of 3.1 eV. Among semiconductor oxides Nb₂O₅ with different morphologies are less explored due to complicated synthesis, growth and nucleation process. Thus, in general, factors involved for self-organized superstructures are not studied in detail. In this context, assembly of T-Nb₂O₅ superstructures is investigated in depth by applying SEM, TEM and UV/Vis absorption measurements. Based on the realized results a formation mechanism is proposed, which is further strengthened by the time and precursor dependent experiments. In addition, asymmetric supercapacitor properties of T-Nb₂O₅ superstructures are studied for the first time by using an inorganic electrolyte. The devised T-Nb₂O₅ superstructures have demonstrated excellent supercapacitor performance. The supercapacitor is operated at a wide potential window of 2.5 V in Na₂SO₄ electrolyte and exhibited high power density (650 W/Kg), energy density (86 Wh/Kg) with good cycling capability.